Last update: November 24, 2010 02:33:41 PM E-mail Print






JH Hoon & PG Marais

Grootfontein Agricultural Development Institute, P/Bag X529, Middelburg E.C., 5900

 email : Jan Hoon


Trace minerals and their functions in the animal become of practical and economical importance only when a deficiency or excess is reflected in deviating animal behaviour, a lower rate of production and reproduction, a recognisable disease syndrome and/or higher than normal rate of mortality. Six trace minerals, namely In, Mn, Cu, Co, Se and I, are generally regarded as important in farm animal nutrition. These trace minerals play an important role in optimal growth, production and reproduction and general health. The most important problem with trace minerals is that deficiencies occur in different grades and that it is very difficult to diagnose a moderate deficiency. Role players in the different small stock industries (wool, meat and mohair) initiated an investigation into the economic advantages of supplementing small stock with different trace minerals. In this study, a commercially manufactured product consisting of a combination of chelated Zn and Mn, as well as Se in the form of sodium selenite, is used. Deficiency symptoms of these three trace minerals are mostly related to low intake and growth rate, decreased immunity, short and irregular oestrus, poor conception especially in young ewes, absorption of fertilised eggs, early born Iambs, etc. The aim of this study is therefore to investigate the effect of trace mineral  supplementation on the production and reproduction rate of small stock and to determine the economic viability of this practice in the different production areas of SA. The study is currently carried out on the farms of 23 participants (15 sheep and 8 goat farmers), using their own animals. At each participant, the ewes were divided into two groups (control and treatment) 4-6 weeks before mating and the animals of the treatment group received a subcutaneous injection of 1 ml of the trace mineral supplement. Ewes were mated as one group, scanned for pregnancy and the treatment group received another trace mineral injection 4-6 weeks before lambing. With the onset of lambing, ewes were placed into two comparable camps until the end of the lambing season. A minimum of 70 ewes per group was used. The following data are collected: scanning percentage, weaning percentage, Iamb mortality rates, body weight of Iambs at 42 days of age and at weaning, body weight of ewes at mating and at 42 day Iamb age. The procedures will be repeated at least three times with the same animals at each locality. Blood samples of 10 animals in each group, as well as soil and water samples, are collected for further analyses. Preliminary results indicate very small or no differences with regard to scanning percentages between the control and treatment groups at most of the localities. In some areas, where shortages of certain trace minerals are common, supplementation increased the conception rate and fecundity of the ewes. The high rainfall that occurred in most of the summer rainfall areas during the mating season, with the resulting good grazing conditions, probably contributed to the small differences observed between the two groups at most of the localities. This project is continuing and will be replicated for at least three years at all the different localities to minimize year effects.